UvumiTools Odometer can be be updated manually or you can set it so it periodically calls a server script via an AJAX request and uses the returned value as a new target. This is also easy, you just need to specify the URL to that script when you initialize the counter. If the difference between two values is too big and the counter is spinning for several minutes. You can directly jump to the targeted value by simply double-clicking on the counter.
Requirements: Mootools 1.2+
License: MIT License